This invention relates to sealing closures for use on containers, such as containers which have neck portions having threads or other configurations adapted to cooperate with similar configurations on the closures. This invention is more particularly directed to linerless closures, those that do not require a separate lining means or gasket to effect a seal on the container.
In the past, linerless closures of a variety of different types have been provided for sealing the open mouth at the upper end of the neck portion of containers. Such closures are generally molded from a plastic material and have a top panel from which a cylindrical skirt extends, the skirt having internal threads adapted to engage similar threads on the external surface of the neck of the container. A variety of different configurations of sealing fins and resilient beads have been suggested to provide a tight seal with the end of the neck of the container when the closure is tightened thereon. In addition, some of the linerless closure configurations require the provision of a special finish on the upper annular rim of the container neck.
One such linerless closure is taught by U.S. Pat. No. 3,255,909 (Ira H. Miller et al), wherein a sealing fin of a specific configuration is adapted to engage an inclined sealing portion on the upper annular rim of the container neck. This particular combination requires the modification of the container neck molds, in order to produce the required taper on the neck finish. In addition, sealing fins of the type disclosed in this patent have been known to experience cold flow or creep, so as to become elongated after they have been applied to the container. This phenomenon sometimes reduces the resiliency of the sealing fin and diminishes the desired tight seal between the sealing fin and the container neck finish.
Another such linerless closure is that disclosed in U.S. Pat. No. 3,814,274 (James A. McIntosh). This patent teaches a linerless closure which may be utilized on a standard container neck finish. It features a pre-bent annular sleeve and an annular bead which deflects outwardly to engage the tip of the annular sleeve to hold it in engagement with the container neck finish. However, because the annular bead is designed to deflect outwardly, only a portion of its flat lower surface engages the annular sleeve when the closure is applied to the container. In addition, the configuration of this flat bottom bead portion is not designed to compensate for cold flow creep or creep of the sealing fin upon repeated application.